Hyperactivity or inappropriate activity of the immune system is a serious and widespread medical problem. It contributes to acute and chronic immune diseases, e.g., allergic and atopic diseases, e.g., asthma, allergic rhinitis, allergic conjunctivitis and atopic dermatitis, and to autoimmune diseases, e.g., rheumatoid arthritis, insulin-dependent diabetes, inflammatory bowel disease, autoimmune thyroiditis, hemolytic anemia and multiple sclerosis. Hyperactivity or inappropriate activity of the immune system is also involved in transplant graft rejections and graft-versus-host disease.
A certain family of transcription factors, the NFAT proteins, are expressed in immune cells and play a key role in eliciting immune responses. The NFAT proteins are activated by calcineurin, and the activated NFAT proteins, in turn, induce transcription of cytokine genes which are required for an immune response. The immunosuppressive drugs cyclosporin A and FK506 are potent inhibitors of cytokine gene transcription in activated immune cells, and have been reported to act by inhibiting calcineurin such that calcineurin is not able to activate NFAT. These drugs, however, can display nephrotoxic and neurotoxic effects after long term usage. Since calcineurin is ubiquitously expressed in many tissues, the drugs' inhibition of calcineurin activity toward substrates other than NFAT may contribute to the observed toxicity.
There is a need for immunosuppressive agents which selectively inhibit the calcineurin-NFAT interactions and which do not inhibit the enzymatic activity of calcineurin for its other substrates.